[Cherry pick] View function Object<T> support (aptos-labs#8051)

* [move-examples] Add view functions to Hero object demo

* [api] Allow Object<T> in view functions

The JSON parsing wasn't working properly for Object<T> so, it now
handles Object types as a one time check, and allows for types to
be provided as well

api/types/src/convert.rs

@@ -37,7 +37,9 @@ use aptos_types::{
 use aptos_vm::move_vm_ext::MoveResolverExt;
 use move_binary_format::file_format::FunctionHandleIndex;
 use move_core_types::{
-    identifier::Identifier,
+    account_address::AccountAddress,
+    ident_str,
+    identifier::{IdentStr, Identifier},
     language_storage::{ModuleId, StructTag, TypeTag},
     value::{MoveStructLayout, MoveTypeLayout},
 };
@@ -50,6 +52,9 @@ use std::{
     sync::Arc,
 };
 
+const OBJECT_MODULE: &IdentStr = ident_str!("object");
+const OBJECT_STRUCT: &IdentStr = ident_str!("Object");
+
 /// The Move converter for converting Move types to JSON
 ///
 /// This reads the underlying BCS types and ABIs to convert them into
@@ -754,7 +759,22 @@ impl<'a, R: MoveResolverExt + ?Sized> MoveConverter<'a, R> {
         type_tag: &TypeTag,
         val: Value,
     ) -> Result<move_core_types::value::MoveValue> {
-        let layout = self.inner.get_type_layout_with_types(type_tag)?;
+        let layout = match type_tag {
+            TypeTag::Struct(boxed_struct) => {
+                // The current framework can't handle generics, so we handle this here
+                if boxed_struct.address == AccountAddress::ONE
+                    && boxed_struct.module.as_ident_str() == OBJECT_MODULE
+                    && boxed_struct.name.as_ident_str() == OBJECT_STRUCT
+                {
+                    // Objects are just laid out as an address
+                    MoveTypeLayout::Address
+                } else {
+                    // For all other structs, use their set layout
+                    self.inner.get_type_layout_with_types(type_tag)?
+                }
+            },
+            _ => self.inner.get_type_layout_with_types(type_tag)?,
+        };
 
         self.try_into_vm_value_from_layout(&layout, val)
     }

api/types/src/move_types.rs

@@ -717,6 +717,7 @@ impl TryFrom<MoveType> for TypeTag {
             MoveType::Signer => TypeTag::Signer,
             MoveType::Vector { items } => TypeTag::Vector(Box::new((*items).try_into()?)),
             MoveType::Struct(v) => TypeTag::Struct(Box::new(v.try_into()?)),
+            MoveType::GenericTypeParam { index: _ } => TypeTag::Address, // Dummy type, allows for Object<T>
             _ => {
                 return Err(anyhow::anyhow!(
                     "Invalid move type for converting into `TypeTag`: {:?}",

aptos-move/move-examples/token_objects/sources/hero.move

@@ -8,13 +8,15 @@ module token_objects::hero {
 
     use aptos_token_objects::collection;
     use aptos_token_objects::token;
+    use aptos_std::string_utils;
 
     const ENOT_A_HERO: u64 = 1;
     const ENOT_A_WEAPON: u64 = 2;
     const ENOT_A_GEM: u64 = 3;
     const ENOT_CREATOR: u64 = 4;
     const EINVALID_WEAPON_UNEQUIP: u64 = 5;
     const EINVALID_GEM_UNEQUIP: u64 = 6;
+    const EINVALID_TYPE: u64 = 7;
 
     struct OnChainConfig has key {
         collection: String,
@@ -158,7 +160,7 @@ module token_objects::hero {
             defense_modifier,
             magic_attribute,
         };
-				move_to(&token_signer, gem);
+        move_to(&token_signer, gem);
 
         object::address_to_object(signer::address_of(&token_signer))
     }
@@ -210,18 +212,60 @@ module token_objects::hero {
         name: String,
         description: String,
     ) acquires Hero {
-        let token_address = token::create_token_address(
+        let (hero_obj, hero) = get_hero(
             &signer::address_of(creator),
             &collection,
             &name,
         );
-        let hero_obj = object::address_to_object<Hero>(token_address);
-        let hero = borrow_global<Hero>(token_address);
         let creator_addr = token::creator(hero_obj);
         assert!(creator_addr == signer::address_of(creator), error::permission_denied(ENOT_CREATOR));
         token::set_description(&hero.mutator_ref, description);
     }
 
+    // View functions
+    #[view]
+    fun view_hero(creator: address, collection: String, name: String): Hero acquires Hero {
+        let token_address = token::create_token_address(
+            &creator,
+            &collection,
+            &name,
+        );
+        move_from<Hero>(token_address)
+    }
+
+    #[view]
+    fun view_hero_by_object(hero_obj: Object<Hero>): Hero acquires Hero {
+        let token_address = object::object_address(&hero_obj);
+        move_from<Hero>(token_address)
+    }
+
+    #[view]
+    fun view_object<T: key>(obj: Object<T>): String acquires Armor, Gem, Hero, Shield, Weapon {
+        let token_address = object::object_address(&obj);
+        if (exists<Armor>(token_address)) {
+            string_utils::to_string(borrow_global<Armor>(token_address))
+        } else if (exists<Gem>(token_address)) {
+            string_utils::to_string(borrow_global<Gem>(token_address))
+        } else if (exists<Hero>(token_address)) {
+            string_utils::to_string(borrow_global<Hero>(token_address))
+        } else if (exists<Shield>(token_address)) {
+            string_utils::to_string(borrow_global<Shield>(token_address))
+        } else if (exists<Weapon>(token_address)) {
+            string_utils::to_string(borrow_global<Weapon>(token_address))
+        } else {
+            abort EINVALID_TYPE
+        }
+    }
+
+    inline fun get_hero(creator: &address, collection: &String, name: &String): (Object<Hero>, &Hero) {
+        let token_address = token::create_token_address(
+            creator,
+            collection,
+            name,
+        );
+        (object::address_to_object<Hero>(token_address), borrow_global<Hero>(token_address))
+    }
+
     #[test(account = @0x3)]
     fun test_hero_with_gem_weapon(account: &signer) acquires Hero, OnChainConfig, Weapon {
         init_module(account);